A merged image of present day Gallipoli and the same scene on 25 April 1915 Australian soldier lies injured in the foreground as troops move among the dead and wounded on the beach at Anzac Cove.
Photograph: Getty Images

What happened?

Anzac Day 2015: centenary of Gallipoli landings - rolling coverage

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In a military disaster 100 years ago, about 58,000 allied soldiers – including 29,000 British and Irish soldiers and 11,000 Australians and New Zealanders – lost their lives on the Gallipoli peninsula. A further 87,000 Ottoman Turkish troops died fighting the allies and at least 300,000 more on both sides were seriously wounded.

What was the objective?

Conceived by Winston Churchill as the First Lord of the Admiralty, the plan was to knock out Ottoman Turkey, Germany’s ally, out of the war. The goal of the naval and land operation was to open up the Dardanelles straits, heavily mined and defended on its western shore by Turkish coastal forts and gun batteries on the 50-mile Gallipoli peninsula, to allied ships, capture Constantinople – present-day Istanbul – and so link up with Russia. Churchill saw the campaign as a way of breaking the attritional deadlock on the western front. “Are there not other alternatives?” he said at the time.

Anzac Cove and Gallipoli: then and now – interactive

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What went wrong?

The repeated British and French bombardments beginning in mid-February against Turkish positions proved ineffective. A final attempt to force a passage up the Dardanelles in March ended in three allied battleships being sunk and three badly damaged. The two landings – one by British troops at Cape Helles, at the base of the peninsula, and the other on the western Aegean coast, in the area later known as Anzac Cove, by the Australian and New Zealand Army Corps – were met by fierce and disciplined Turkish opposition. Well dug in and heavily fortified on higher ground, they had been reinforced six times over. The allies had badly underestimated the capacity of the Turkish forces.

How much headway did the allies make?

Most did not advance more than a few hundred metres from the shore where they were pinned down. The allies endured suffocating heat and were surrounded by rotting corpses that drew thick swarms of flies. They lacked water and thousands died from dysentery as disease spread. The campaign did divert large Turkish forces away from the Russians, but did not produce the desired strategic success.

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How did the campaign end?

The allied commander, Sir Ian Hamilton, was replaced by Sir Charles Munro and the allies withdrew in January 1916. In contrast to the attack the retreat was considered a major success. Churchill resigned from the government and went to command an infantry battalion in France. The disaster hastened Asquith’s resignation and his replacement as prime minister by David Lloyd George.

What is Gallipoli’s legacy?

The Australian prime minister, Tony Abbott, said it “left horrific scars and was, in a critical sense, our nation’s baptism of fire – and 8,000 Australians didn’t come back”. Anzac day on 25 April – in remembrance of the Gallipoli campaign – is one of Australia’s most important national occasions. For Turkey, the victory saw the triumph of Mustafa Kemal, a 33-year-old lieutenant colonel who commanded the 19th Turkish Division and famously told his men: “I don’t order you to attack; I order you to die.” As Mustafa Kemal Atatürk, he became the founding father of the Turkish republic in 1923.